The dielectric coatings used in the current generation of GW detectors are Bragg reflectors [1]} made of alternate ion-beam sputtered (IBS) thin layers of silica (SiO\(_2\) ) and tantala-titania (Ta\(_2\) O\(_5\) -TiO\(_2\) ). Silica is the low refractive index material (\(n = 1.45\)  at 1064 nm), and the tantala-titania is the high refractive index material (\(n = 2.07\)  at 1064 nm) [2]}. These materials and their synthesis by various methods have been extensively investigated in the context of optical materials in general and interferometric filters in particular [1]}, including for example their mechanical properties [4]}, [5]}, [2]}, showing that their performance is intimately related to parameters such as their internal stress and growth parameters [2]}.
